(i) Field of the Invention
This invention relates to the smelting of metal with oxygen.
(ii) Description of the Prior Art
U.S. Pat. No. 3,706,549, the teaching of which is hereby incorporated herein by reference describes the injection of oxygen into a bath of molten metal from below the bath surface in the refining of pig-iron to steel, such that accelerated erosion of the refractory used to line the container of the bath is prevented.
The oxygen injector, which extends through the refractory wall lining of the container, comprises two concentric tubes. The inner tube is used for the injection of oxygen and the annular space between the inner tube and the outer tube is for applying a protective fluid. The fluid which is usually a hydrocarbon, is employed to shield the oxygen from the reactive molten metal at the interface of the refractory wall and the molten metal and ensures that the vigorous reaction with the molten metal takes place away from the refractory wall. The resultant delay in the exothermic reaction between the oxygen and the molten metal is sufficient to maintain the integrity of the refractory wall.
It is also known, in the refining of pig iron to steel, to introduce a flux to the oxygen stream enabling the flux, the molten metal and oxygen gas to be in close proximity for efficient flux utilization and for efficient refining of the molten pig iron.
The fluxes conventionally used in the refining of pig iron to steel, which fluxes include lime, spar and dolomite, are not reactive to oxygen gas and hence pneumatic transfer of the flux in the gaseous oxygen stream is acceptable.
In the case of fluxes which are reactive with oxygen, it is not safe to pneumatically convey the flux in an oxygen stream.
In the direct smelting of lead sulphide concentrates, as described in U.S. Pat. No. 3,281,237 - Meissner, the teaching of which is hereby incorporated herein by reference, particulate lead sulphide is pneumatically conveyed with air into a molten lead bath with the appropriate ratio of oxygen in the air to carry out the smelting reaction.
It would be extremely hazardous to pneumatically convey the particulate lead sulphide concentrate in an oxygen stream because of the highly explosive nature of the mixture.
It is an object of this invention to provide a method of pneumatically introducing a metal ore which is reactive with oxygen into a molten metal simultaneously with the injection into the molten metal of oxygen.